These are desperate days for Man United: After derby defeat and academy star JJ Gabriel's public snub, it gets even worse for Michael Carrick as Brighton fight back to knock them out of the Carabao Cup

What desperate days these are for Manchester United. Beaten here in the Old Trafford derby on Sunday, at odds with supporters and in danger of losing the crown jewel of their academy, they crashed out of the Carabao Cup at the first attempt for the second year in a row. At least Brighton aren’t Grimsby.

The night had started so positively as well. Leading 2-0 inside 10 minutes, United looked to be cruising into the fourth round. Better still, the scorer of the first goal on his first start was teenager Shea Lacey who couldn’t have timed it more perfectly following the bombshell news on Tuesday that his Under-21s teammate JJ Gabriel wants to quit the club.

But it has been a poor start to the new season for Michael Carrick’s side, and it was about to get even worse as Brighton fought back to stun Old Trafford with their fifth win here in six visits.

It was also the first time in 50 years and 146 games that United have lost at home after being two goals ahead, going back to a 3-2 defeat to Tottenham in September, and the first after leading at half-time since Ipswich won here in 1984.

After a tame defeat in the derby to Manchester City on Sunday that could not be hidden behind the VAR controversy over Erling Haaland’s winning goal, this was a second defeat in four days at Old Trafford.

The boos at full-time told their own story. Carrick takes his team to Fulham on Sunday knowing that another one will put him under close early-season scrutiny going into the long international break.

‘We can't accept that as a group,’ said the United boss. ‘I take responsibility for it. It's on me ultimately. I’ll take the praise, I’ll take the criticism and the upset.

‘The pressure doesn’t bother me one bit. I understand how the world works. The feeling at the start of the game to the feeling at the end couldn’t be further apart. It’s happened so quickly over two or three weeks, there’s a lot of disappointment.

‘Of course we can turn it around. We have to be better. It doesn't feel good at the moment. We have a big game on Sunday that we have to go back to winning football matches.’

On the furore over Gabriel, Carrick added: ‘We have to be a little bit careful on that one. He's a 15-year-old boy. It's more about the welfare, the care and the attention of JJ as a child really.’

The news about Gabriel could hardly have come at a worse time. Lacey appeared to react to it on Tuesday night by posting a photo of himself walking into Old Trafford along with a heart emoji, and he made another point inside eight minutes when he fired United ahead.

It was a particularly sweet moment for the 19-year-old given that he was sent off against Brighton on his home debut as a substitute in January.

There was something inevitable about his goal last night. Youri Tielemans picked out Lacey on the right side of the box and he cut inside Jaouen Hadjam before whipping a shot inside Jason Steele’s near post.

Old Trafford rose to salute the first teenager to score on his United debut since Marcus Rashford against Midtjylland here a decade ago.

The fans had only just settled down when Mason Mount had them off their seats again in the 10 minute. Rashford picked Costinha’s pocket and breezed past Luka Vuskovic. Steele kept out his effort but the ball ran to Mount who got there just ahead of Lacey to score the second.

At that stage, who could have foreseen the pain that was about to follow?

United were enjoying themselves and the crowd loved it when Rashford, who had Costinha on the run down the left, nutmegged Chema Andres.

But there was a vulnerability to them that was perhaps epitomised by the young centre-back partnership of Ayden Heaven and Leny Yoro after Carrick made eight changes from the derby and waited too long to change back again as the tide of the game turned dramatically against his team.

‘The performance towards the end of the first half is on me,’ he admitted after Brighton took control and threatened on a number of occasions before Charalampos Kostoulas pulled a goal back in added time at the end of the half. 

United were unhappy that referee Farai Hallam didn’t give Benjamin Sesko a free kick when he was floored by a tag team of Malick Yalcouye and Olivier Boscagli, but they switched off as Hadjam’s long diagonal pass picked out Kostoulas who got in between Heaven and Darlow to score.

The equaliser arrived in the 64th minute when Diogo Dalot hooked a clearance towards halfway where Sesko was under pressure by Pascal Struijk and succeeded only in heading the ball 30 yards back towards his own goal. Pascal Gross was waiting to receive it on the edge of the box and sold Yoro a dummy before sliding a shot past Darlow.

The momentum was with Brighton and Kostoulas got away from Mazraoui in the 69th minute and crossed for substitute Maxim De Cuyper to complete an incredible comeback.

‘I definitely believed and belief was a big word in the preparation for us,’ said head coach Fabian Hurzeler. ‘When you go to a place like this you need to have belief and then to show it when you are two goals down shows real character.'